The oxo process is the commercial application of the hydroformylation reaction for making higher alcohols and aldehydes from olefins. In the cobalt oxo process, an olefin reacts with carbon monoxide and hydrogen (i.e., syn gas) at elevated temperatures in the presence of a cobalt carbonyl catalyst to produce a hydroformylation reaction product which is subsequently decobalted or demetalled to produce a crude product mixture of aldehydes, alcohols, acetals, formates, unreacted olefins and secondary products. Subsequent hydrogenation steps provide the desired finished alcohol products commonly referred to as oxo alcohols (i.e., alcohols produced by an oxonation reaction).
One aspect of the overall cobalt oxo process involves the preparation of the active cobalt catalyst species which is hydrido cobalt carbonyl (HCo(CO).sub.4). Commercial oxo processes employ a preforming step in which this active cobalt catalyst species is prepared using a noble metal preforming catalyst which is contacted with a cobalt salt, e.g., cobalt formate, to provide the desired HCo(CO).sub.4 species.
This preforming step is disclosed, for example, in U.S. Pat. No. 4,404,119, which issued Sep. 13, 1983, to Lagace et al. and in U.S. Pat. No. 4,255,279, which issued Mar. 10, 1981, to Spohn et al.
The present inventors have developed an improvement in the process for preparing oxo alcohols by the cobalt catalyzed hydroformylation of C.sub.2 to C.sub.17 linear or branched monoolefins with subsequent hydrogenation of the hydroformylation reaction product which has been disclosed in co-pending U.S. patent application, Ser. No 08/122,859, filed on Sep. 16, 1993 now U.S. Pat. No. 5,321,168. In this co-pending application the aqueous solutions of cobalt salts have been converted to active hydrido cobalt carbonyl species in a preformer reactor, the preformer containing (i) preformer metal catalyst of Group IB or VIII of the Periodic Table or (ii) a preformer non-metallic catalyst selected from the group consisting of activated carbon, ion exchange resins, silica alumina and zeolites. The preformer catalyst was reactivated according to co-pending U.S. patent application, Ser. No. 08/122,859 by treating it at a temperature of about 120.degree. C. to 170.degree. C. and at a pressure of about 13.78 MPa (2,000 psig) to 31.00 MPa (4,500 psig) and preferably about 20.67 MPa (3,000 psig), with water or with a mixture of water and hydrogen or a mixture of water and syn gas for a period of about 2 to 50 hours, whereby the conversion of the cobalt salts to hydrido cobalt carbonyl is improved when such salts are contacted with the treated preformer catalyst.
However, the reactivation process according to copending U.S. patent application, Ser. No. 08/122,859, requires that the preformer solvent or organic feed stream to the preformer reactor be shutoff in order for the catalyst to be treated. This is both time consuming and inefficient.
The present invention does not require shutting off the preformer solvent or organic feed stream during reactivation of the preformer catalyst, but makes use of a readily available preformer solvent in the reactivation step. The preformer solvent (e.g., hexyl alcohol) also allows for the dissolution of organic foulants contained within the pores of the catalyst, thus making it easier for water to enter each pore. It is desirable to have water in the pores during reaction since the Co.sup.2+ reactant material is in the water phase. The aqueous formic acid solution allows for the dissolution of any deposited cobalt compounds that may deactivate or foul active catalytic sites.